As the method of producing adamantanepolyols, proposed are a method using chromic acid (Japanese Patent Application Laid-Open No. 2-104553), hydrolysis of a brominated adamantane (Japanese Patent Application Laid-Open No. 3-118342 and Japanese Patent No. 26787849), air-oxidation of adamantane compounds in the presence of imide compound catalyst (Japanese Patent Application Laid-Open Nos. 8-38909, 9-327626 and 10-286467), metalloporphyrin-catalyzed oxidization of adamantane compounds by air (Japanese Patent Application Laid-Open No. 9-87216), a method of using ruthenium catalysts and peroxy acids (Japanese Patent Application Laid-Open No. 5-51334), a method of using dioxirane derivatives (J. Am. Chem. Soc., 111, 6749 (1989)), etc. However, the major problems of the proposed methods are in the complicated reaction systems and low yields.
In U.S. patent application Ser. No. 09/493,207 (European Patent Application No. 00100253.4), the inventors have proposed a process for producing adamantanols in high yields by hydroxylation of adamantane compounds in a water/organic two-phase system in the presence of a ruthenium compound and a salt of hypochlorous acid. The ruthenium used in the process is a very expensive transition metal. Therefore, loss of the ruthenium compound must be minimized in the production of adamantanols and it is quite important for the industrial application of the process to ensure the recovery and reuse of the ruthenium compound.